1. Field of the Invention
This invention relates to a video signal processor having an oscillation circuit for generating a reference signal or the like using a crystal unit.
2. Description of the Related Art
A video cassette recorder uses a microcomputer for controlling the operation of the main unit and the rotation speed of a capstan motor and the like. The microcomputer is adapted to also keep the time of day at the power outage time when the commercial power supply is stopped.
FIG. 1 shows the related art for performing the above operation, wherein a microcomputer 291 is provided with two oscillation circuits 295 and 296. A 32.768-kHz crystal unit 292 is connected to the oscillation circuit 295 and a 12-MHz crystal unit 293 is connected to the oscillation circuit 296.
In the operation standby state, only the oscillation circuit 295 is operated and an output thereof is led to a central processing unit (CPU) 297. Thus, the microcomputer 291 performs the time-keeping operation with less power consumption, and also performs the control operation required in the standby state.
On the other hand, when the operation state is entered, an output of the oscillation circuit 296 is led to the CPU 297. Thus, the microcomputer 291 performs the high-speed operation in accordance with a high-frequency clock signal for controlling the rotation speed of the capstan motor and the like, or other operations.
As described above, the crystal unit 292 for generating a clock signal in the standby state and the crystal unit 293 for generating a clock signal in the operation state are connected to the microcomputer 291. That is, the microcomputer 291 requires two crystal units 292 and 293. However, since the crystal units 292 and 293 are expensive devices, use of the two crystal units 292 and 293 results in a rise in cost of the video cassette recorder.
To enhance accuracy and stability of the receiving frequencies, a video signal receiver such as a video cassette recorder, a television set, and the like, uses a phase locked loop (PLL) circuit to generate a local oscillation signal of a predetermined frequency for determining the receiving frequency. In such a configuration, a reference signal for making a phase comparison with an output of a local oscillation circuit is indispensable. Thus, in a conventional receiver, the PLL circuit is provided with an exclusive crystal unit for generating the reference signal.
However, the crystal unit is an expensive device as described above and in case of using a PLL circuit for determining the receiving frequency, the number of crystal units to be used is increased, resulting in a rise in cost of the system.
FIG. 2 is a block diagram showing the configuration of a conventional video cassette recorder with a television set. That is, a tuner unit 391 takes out a video signal from a received signal and sends the taken-out video signal to a recording/reproducing unit 396. At the operation time except reproduction, a video signal processing unit 393 generates primary-color chrominance signals of R, G, and B from the video signal received through the recording/reproducing unit 396 from the tuner unit 391. A cathode-ray tube (CRT) unit 394 amplifies the primary-color chrominance signals generated by video signal processing unit 393 to a predetermined level and drives a CRT by the amplified primary-color chrominance signals. At the recording time, the recording/reproducing unit 396 applies predetermined processing to the video signal for generating a signal to be recorded, and feeds the generated signal into a rotary head 397. At the reproducing time, the recording/reproducing unit 396 applies predetermined processing to a reproduced signal output from the rotary head 397 for reproducing the video signal, and outputs the reproduced video signal to the video signal processing unit 393. As a result, an image is displayed on the CRT unit 394 by the reproduced video signal.
In the operation described above, the video signal processing unit 393 requires a signal (reference subcarrier) phase-synchronized with a burst signal in the video signal. Thus, the video signal processing unit 393 uses a crystal unit 395 to generate a reference subcarrier. The recording/reproducing unit 396 requires a reference subcarrier at the recording time and a reference signal used as reference of a burst signal at the reproducing time. Thus, the recording/reproducing unit 396 uses a crystal unit 398 to generate a reference subcarrier at the recording time and a reference signal at the reproducing time. The crystal units 395 and 398 are connected to the video signal processing unit 393 and the recording/reproducing unit 396 respectively. However, since the crystal units are expensive devices as described above, use of two crystal units results in a rise in the total cost of the parts to be used, raising a large bottleneck for reducing the manufacturing cost.